Printers are typically required to handle print media of various widths. Lateral alignment of print media across the print head may be accomplished by one of two means: (a) a single edge-justified means, in which regardless of the print media width, one edge of the print media occupies the same position across the print head, or (b) a center-justified means, in which regardless of the print media width, the center of the print media always aligns with the center of the print head. The latter is generally preferred by printer manufacturers from a mechanical standpoint as it provides better media tracking, more even pressure, and the like.
FIGS. 1–2 schematically illustrate a conventional center-justified media guide holder setup in which two opposing print media guide members 10, 12 are operatively coupled via integral racks 16, 18, respectively, and a single central pinion 14. Each rack is provided on one side with a plurality of teeth which mesh with a corresponding set of teeth on central pinion 14. Print media guide members 10, 12 are adapted to move in a reciprocal linear fashion relative to each other to afford a range of print media widths. Typical minimum/maximum media widths (capture ranges) may be, for example, 1 inch and 1.875 inch, respectively, as generally shown in FIGS. 1–2. Pinion 14 is adapted to rotate on a fixed post 20 (FIGS. 1–2) which is mounted centrally between print media guide members 10, 12 on a printer frame (not shown).
In any given design there will be a minimum and a maximum media capture range for the purpose of accommodating a range of media widths. In portable printers, design options are substantially influenced by available space which is minimal due to the need to make the printer as small as possible. It would be desirable to increase the maximum media capture range to accommodate wider media without making substantial modifications to the overall printer design.